Process for preparing sintered shaped and articles so prepared thereby

Abstract

The invention relates to a method of preparing sintered shapes, comprising the steps of: (1) forming a green body from a mixture comprising (A) at least one inorganic powder with (B) at least one polymer derived from (a) at least two sulfo monomers or (b) a combination of (i) a sulfo monomer with (ii) at least one monomer selected from acrylic compounds, acrylonitriles, vinyl lactams and vinyl pyrrolidones and maleic acids, anhydrides or salts, provided the mixture is substantially free of polysaccharide; (2) sintering the body. Inorganic shapes made from the compositions of the present invention have relatively high fired densities; small uniform grain sizes; and relatively low porosity. The sulfo polymers of the present invention help disperse the inorganic powder. These polymers improve deagglomeration of the inorganic powder and also help prevent reagglomeration of the powder. The polymers provide divalent ion stability for systems using water containing divalent ions, such as hard water. These polymers help reduce viscosity of inorganic powder slurries and improve defloculation of the inorganic powder.

We claim: 
     
       1. A method of preparing sintered shapes, comprising the steps of: (1) forming a green body from a mixture comprising (A) at least one inorganic powder with (B) at least one polymer derived from (a) at least two sulfo monomers or (b) a combination of (i) at least one sulfo monomer and (ii) at least one comonomer selected from the group consisting of acrylic compounds; maleic acids, anhydrides or salts; vinyl lactams; vinyl pyrrolidones; and fumaric acids or salts, provided the mixture is substantially free of polysaccharides.   (2) sintering the body.   
     
     
       2. The method of claim 1 wherein the sulfo monomer is selected from vinylalkyl sulfo monomer and vinylaryl sulfo monomer. 
     
     
       3. The method of claim 1, wherein the sulfo monomer is an acrylamidohydrocarbyl sulfo monomer. 
     
     
       4. The method of claim 1, wherein the sulfo monomer is 2-acrylamido-2-methylpropane sulfonic acid or at least one salt thereof. 
     
     
       5. The method of claim 1, wherein the sulfo monomer is represented by the formula ##STR5## or mixtures thereof, wherein each R 1  is independently hydrogen or a hydrocarbyl group; a is 0 or 1; b is 1 or 2, provided that when a is 0, then b is 1; Q is a divalent or trivalent hydrocarbyl group or C(X)NR 2  Q';   each R 2  is independently hydrogen or a hydrocarbyl group;   Q' is a divalent or trivalent hydrocarbyl group;   X is oxygen or sulfur;   Z is S(O)O, or S(O) 2  O; and   M is hydrogen, a metal cation or ammonium cation.   
     
     
       6. The method of claim 5, wherein a and b are one; Q is C(X)NR 2  Q'; X is oxygen; Q' is an alkylene group having 1 to about 18 carbon atoms; and Z is SO 2  O. 
     
     
       7. The method of claim 1, wherein the polymer (B) contains a sulfo-ammonium salt which is derived from ammonia or an amine. 
     
     
       8. The method of claim 7, wherein the sulfo-ammonium salt is formed from an alkanolamine. 
     
     
       9. The method of claim 8, wherein the alkanolamine is diethylethanolamine or aminomethylpropanol. 
     
     
       10. The method of claim 1, wherein the polymer (B) contains a sulfo-metal salt wherein the metal of the metal salt is an alkali, alkaline earth or transition metal. 
     
     
       11. The method of claim 1, wherein the polymer (B) is an polymer of (i) the sulfo monomer and (ii) at least one comonomer selected from an acrylic acid, ester or salt; a methacrylic acid, ester or salt; an acrylamide; and a maleic acid, ester or anhydride. 
     
     
       12. The method of claim 1, wherein the comonomer (ii) is an acrylic acid, ester or salt. 
     
     
       13. The method of claim 1, wherein the interpolymer is prepared by polymerizing from about 10 mole percent to about 90 mole percent of the sulfo monomer (i) with from about 10 mole percent to about 90 mole percent of the comonomer (ii). 
     
     
       14. The method of claim 1, wherein the interpolymer is prepared by polymerizing from about 20 mole percent to about 75 mole percent of the sulfo monomer (i) with from about 25 mole percent to about 80 mole percent of the comonomer (ii). 
     
     
       15. The method of claim 1, wherein the polymer (B) is present in an amount from about 0.01% to about 30% by weight, based on the inorganic powder (A). 
     
     
       16. The method of claim 1, wherein the inorganic powder (A) is alumina or clay. 
     
     
       17. The process of claim 1, wherein the mixture of step (1) further comprises water. 
     
     
       18. The method of claim wherein step (2) further comprises removing volatile material from the shape. 
     
     
       19. A method for preparing sintered shapes, comprising the steps of: (1) forming a green body from a mixture comprising (A) at least one inorganic powder; (B) at least one polymer derived (i) from at least one acrylamidohydrocarbyl sulfo monomer and (ii) at least one comonomer selected from acrylic compounds, acrylonitriles, vinyl lactams, vinyl pyrrolidones and maleic acids, anhydrides or salts; and water, provided the mixture is substantially free of polysaccharide;   (2) sintering the body.   
     
     
       20. The method of claim 19, wherein the sulfo monomer is 2-acrylamido-2-methylpropane sulfonic acid. 
     
     
       21. The method of claim 19, wherein the polymer (B) contains a sulfo-ammonium salt which is derived from ammonia, a monoamine or a polyamine. 
     
     
       22. The method of claim 21, wherein the sulfo-ammonium salt is derived from a hydroxyamine. 
     
     
       23. The method of claim 22, wherein the hydroxyamine is aminomethyl propanol. 
     
     
       24. The method of claim 19, wherein the polymer (B) is prepared by polymerizing from about 25 mole percent to about 75 mole percent of an acrylamido hydrocarbyl sulfo monomer (i), and from about 25 mole percent to about 75 mole percent of acrylic acid, ester or salt (ii). 
     
     
       25. The method of claim 19, wherein the inorganic powder (A) is a alumina or clay. 
     
     
       26. The process of claim 19, wherein step (2) further comprises removing volatile material from the shape. 
     
     
       27. An article, comprising:  a green body comprising a major amount of (A) at least one inorganic powder and (B) at least one polymer derived from (i) at least one sulfo monomer and (ii) at least one monomer selected from acrylic compounds, acrylonitriles, vinyl lactams, vinyl pyrolidones and maleic acids, anhydrides or salts.   
     
     
       28. The article of claim 27, wherein the sulfo monomer is an acrylamidohydrocarbyl sulfo monomer. 
     
     
       29. A sintered shape prepared by the method of claim 1.